SUMO Modification of the RNA-Binding Protein La Regulates Cell Proliferation and STAT3 Protein Stability.

The cancer-associated RNA-binding protein La is posttranslationally modified by phosphorylation and sumoylation. Sumoylation of La regulates not only the trafficking of La in neuronal axons but also its association with specific mRNAs. Depletion of La in various types of cancer cell lines impairs cell proliferation; however, the molecular mechanism whereby La supports cell proliferation is not clearly understood.

Applying a high-throughput fluorescence polarization assay for the discovery of chemical probes blocking La:RNA interactions in vitro and in cells.

The RNA-binding protein La is overexpressed in a number of tumor tissues and is thought to support tumorigenesis by binding to and facilitating the expression of mRNAs encoding tumor-promoting and anti-apoptotic factors. Hence, small molecules able to block the binding of La to specific RNAs could have a therapeutic impact by reducing the expression of tumor-promoting and anti-apoptotic factors. Toward this novel therapeutic strategy, we aimed to develop a high-throughput fluorescence polarization assay to screen small compound libraries for molecules blocking the binding of La to an RNA element derived from cyclin D1 mRNA.

SUMO-Modification of the La Protein Facilitates Binding to mRNA In Vitro and in Cells.

The RNA-binding protein La is involved in several aspects of RNA metabolism including the translational regulation of mRNAs and processing of pre-tRNAs. Besides its well-described phosphorylation by Casein kinase 2, the La protein is also posttranslationally modified by the Small Ubiquitin-like MOdifier (SUMO), but the functional outcome of this modification has not been defined. The objective of this study was to test whether sumoylation changes the RNA-binding activity of La.

The La protein counteracts cisplatin-induced cell death by stimulating protein synthesis of anti-apoptotic factor Bcl2.

Up-regulation of anti-apoptotic factors is a critical mechanism of cancer cell resistance and often counteracts the success of chemotherapeutic treatment. Herein, we identified the cancer-associated RNA-binding protein La as novel factor contributing to cisplatin resistance. Our data demonstrate that depletion of the RNA-binding protein La in head and neck squamous cell carcinoma cells (HNSCC) increases the sensitivity toward cisplatin-induced cell death paralleled by reduced expression of the anti-apoptotic factor Bcl2.

2'-Hydroxy ceramide in membrane homeostasis and cell signaling.

Ceramide is a precursor of complex sphingolipids and also plays important roles in cell signaling. With the advances in lipid analytical technologies, the structural diversity of ceramide species have become evident, and the complexity of cellular metabolism and function associated with distinct ceramide species is beginning to be revealed. One of the common structural variations of ceramide is 2'-hydroxylation of the N-acyl chain.

2'-hydroxy C16-ceramide induces apoptosis-associated proteomic changes in C6 glioma cells.

Ceramide is a bioactive sphingolipid involved in regulation of numerous cell signaling pathways. Evidence is accumulating that differences in ceramide structure, such as N-acyl chain length and desaturation of sphingoid base, determine the biological activities of ceramide. Using synthetic (R)-2'-hydroxy-C16-ceramide, which is the naturally occurring stereoisomer, we demonstrate that this ceramide has more potent pro-apoptotic activity compared to its (S) isomer or non-hydroxylated C16-ceramide.

Identification of C(6) -ceramide-interacting proteins in D6P2T Schwannoma cells.

Ceramide is a bioactive molecule involved in numerous cell signaling pathways that are associated with cell cycle control, differentiation, senescence, and apoptosis. Although substantial knowledge about ceramide-regulated pathways has accumulated in the past decade, molecular mechanisms of ceramide action remain poorly understood, primarily due to limited information about ceramide-binding proteins. In the present study, we used affinity purification with a synthetic biotin-conjugated C(6) -ceramide analogue and LC-MS/MS to identify potential ceramide-interacting proteins in D6P2T Schwannoma cells.

Proteome of human endometrium: Identification of differentially expressed proteins in proliferative and secretory phase endometrium.

Purpose: To exploit the potential of proteomics to identify and study additional yet-unidentified important proteins present in human endometrium.

Experimental Design: The proteome of human endometrium would be established using 2-DE and MALDI and the data analyzed to identify differential protein expression in the proliferative and secretory phase of the menstrual cycle using PDQuest software and MALDI.

Results: In the present work, 2-DE of human endometrium protein led to the resolution of over 200 spots.

Differential proteome profiling of eutopic endometrium from women with endometriosis to understand etiology of endometriosis.

The identification of molecular differences in the endometrium of women with endometriosis is an important step toward understanding the pathogenesis of this condition and for developing novel strategies for the treatment of associated infertility and pain. In this study, we investigated protein expression analysis of eutopic endometrium from women with and without endometriosis. The proteomic analysis revealed molecular dysregulation of more than 70 proteins in the proliferative phase of eutopic endometrium in stage IV and secretory phase of stage II, III and IV endometriosis.

Role of glycerol-3-phosphate dehydrogenase 2 in mouse sperm capacitation.

A tyrosine phosphoproteome study of hamster spermatozoa indicated that glycerol-3-phosphate dehydrogenase 2 (GPD2), is one of the proteins that enables tyrosine phosphorylation during sperm capacitation. Further, enzymatic activity of GPD2 correlated positively with sperm capacitation [Kota et al., 2009; Proteomics 9:1809-1826].

Glucose-regulated protein precursor (GRP78) and tumor rejection antigen (GP96) are unique to hamster caput epididymal spermatozoa.

The immotile testicular mammalian spermatozoon gets transformed into a motile spermatozoon during 'epididymal maturation'. During this process, the spermatozoa transit from the caput to the cauda epididymis and undergo a number of distinct morphological, biophysical and biochemical changes, including changes in protein composition and protein modifications, which may be relevant to the acquisition of motility potential. The present proteome-based study of the hamster epididymal spermatozoa of caput and cauda led to the identification of 113 proteins spots using Matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS) analysis.

The role of mitochondrial proteins in sperm capacitation.

Spermatozoa deposited in the female reproductive tract need to undergo a multifaceted maturation process prior to fertilization termed "capacitation". This process is regulated by several proteins which are compartmentalized in discrete domains of the spermatozoon including the head, the mid-piece and the principal piece. Over the last decade many proteins involved in capacitation have been identified, such as proteins involved in the organization of the tail, proteins involved in signal transduction, chaperones, ion-channel proteins and mitochondria-associated proteins.

Tyrosine phosphoproteome of hamster spermatozoa: role of glycerol-3-phosphate dehydrogenase 2 in sperm capacitation.

Capacitation confers on the spermatozoa the competence to fertilize the oocyte. At the molecular level, a cyclic adenosine monophosphate (cAMP) dependent protein tyrosine phosphorylation pathway operates in capacitated spermatozoa, thus resulting in tyrosine phosphorylation of specific proteins. Identification of these tyrosine-phosphorylated proteins and their function with respect to hyperactivation and acrosome reaction, would unravel the molecular basis of capacitation.

Hamster sperm capacitation: role of pyruvate dehydrogenase A and dihydrolipoamide dehydrogenase.

Recently, we demonstrated that pyruvate dehydrogenase A2 (PDHA2) is tyrosine phosphorylated in capacitated hamster spermatozoa. In this report, using bromopyruvate (BP), an inhibitor of PDHA, we demonstrated that hamster sperm hyperactivation was blocked regardless of whether PDHA was inhibited prior to or after the onset of hyperactivation, but the acrosome reaction was blocked only if PDHA was inhibited prior to the onset of the acrosome reaction. Further, inhibition of PDHA activity did not inhibit capacitation-associated protein tyrosine phosphorylation observed in hamster spermatozoa.

Penetrating gastric ulcer presenting as a subcapsular liver abscess.

This report describes a subcapsular liver abscess secondary to a penetrating gastric ulcer. The initial read on the CT scan misinterpreted the abscess cavity as an opacified loop of bowel, although it was very conspicuous on a retrospective review. A penetrating gastric ulcer was identified with esophagogastroduodenoscopy and the subcapsular liver abscess was subsequently detected using MRI.

Outcomes of management in stable children with intra-abdominal free fluid without solid organ injury after blunt abdominal injury.

Background: The optimal management of hemodynamically stable children without solid-organ injury and with intra-abdominal free fluid on computed tomographic (CT) scan is highly debatable. The possibility of hollow viscus injury in this setting has led many to propose mandatory exploration. We think that stable children with intra-abdominal fluid without solid organ injury can be managed nonoperatively.

Gastric bypass for morbid obesity in patients 50 years or older: is laparoscopic technique safer?

Some physicians have considered age > or = 50 years as a relative contraindication for bariatric surgery. Recent reports demonstrated the safety and efficacy of Roux-en-Y gastric bypass (RYGB) in this patient subgroup, but comparisons between laparoscopic technique (LT) and open technique (OT) have not been reported. A review of 52 patients > or = 50 years old who underwent RYGB between January 1999 and April 2002 was conducted.

Gastrojejunostomy during laparoscopic gastric bypass: analysis of 3 techniques.

Hypothesis: Although perceived as a more technically demanding and time-consuming technique, the hand-sewn gastrojejunostomy during laparoscopic Roux-en-Y gastric bypass (RYGB) is associated with fewer complications and lower costs than stapled techniques.

Design: A retrospective medical record review of prospectively collected data.

Setting: University hospital.